Jane Straus - Problems with Prepositions

Jane Straus is the author of The Blue Book of Grammar and Punctuation and developer of GrammarBook.com

Prepositions are words that often show direction: below, above, over, under, around, through,
in, out, between, among, to, toward(s). Other common prepositions include of, for (also sometimes a conjunction), from, with, like (also sometimes a
verb).

Rule 1:
You shouldn’t use unnecessary prepositions.

Incorrect:Where did he go to?

Correct:Where did he go?

To is
unnecessary because the meaning is clear without it.

Incorrect: I
don’t know where my jacket is at.

Correct: I
don’t know where my jacket is.

Incorrect: Please
get the cat off of the table.

Correct: Please
get the cat off the table.

Rule 2. Many
of us learned that it is always incorrect to end a sentence with a preposition.
This is a myth! The rule actually states that it is incorrect to end a sentence
with an unnecessary preposition.
Sentences may end with necessary prepositions.

Correct:That is something I cannot agree with.

Even
though you could rewrite the sentence so that with does not end the sentence
(That is something with which I cannot agree.), it is not incorrect to end this
sentence with a preposition because it is a necessary one.

Correct:How many of you
can I count on?

On is a necessary preposition. Alternately, you could write the sentence
this way:

On
how many of you can I count? But doesn’t this tortured phrasing to avoid ending
a sentence with a preposition seem absurd?